The present disclosure relates generally to DC/DC resonant converters, and more specifically, a wide input DC/DC resonant converter that limits reactive power.
Conventional DC/DC switched-mode power converters, and in particular resonant converters, often use phase-shift modulation (PSM) control that reduce switching losses and noise by operating in a Zero-Voltage Switching (ZVS) mode. The ZVS mode may be utilized with a high switching frequency to provide a compact and low-loss power converter. During light load conditions the ZVS mode becomes ineffective, and in high input line conditions excessive reactive power occurs.
A conventional method of improving ZVS during light load conditions is to introduce an additional inductive current, i.e., a lagging current source, into the converter nodes coupled to the switching transistors. The lagging current source extends the range of low-loss switching to light loads, but often compromises efficiency at mid-range and full loads. For example, conventional series resonant converter (SRC) topologies are designed to deliver the full rated power at the lowest input voltage. However, the power stored in the resonant tank at any given half-cycle interval is proportional to the square of the input voltage. Consequently, in full-load conditions, any increase of the input voltage generates both reactive power and circulating currents that reduces efficiency at high input voltages.